File Formats: Source Table: Observations
This document describes the column content of the observation extension (HDU2) within the FITS format version of the UV catalogue. This extension records descriptive details of each observation included within the the catalogue. In version 1.O, 2388 observations have been ingested into the catalogue and a description of the selection and screening of data is provided in the Data Selection section. Each column name listed below may also be followed with terms in round () or square [] brackets. The first brackets contain the form of the column data in FITS nomenclature. J represents a 4-byte integer, E is a 4-byte floating point number, D is a 8-byte double precision number and nA is a character string where n is the maximum length allowed for the string. The square brackets contain the units of the data, where appropriate.
A number of columns report the same quality but for different instrument filters. For the sake of efficiency, these descriptions are not repeated six times i.e. once per filter. When the word FILTER is encountered within column descriptions you will find six columns within the table in which the word "FILTER" can be replaced by one of "UVW2", "UVM2", "UVW1", "U", "B" or "V", the broadband filter sequence of the OM.
Beyond column descriptors, there are no additional non-standard keywords within the extension header structure.
- N_SUMMARY (J)
This is a reference number. HDU2 of the source catalogue contains a summary of the XMM pointings included within the catalogue. Each row of HDU2 refers to a specific pointing and also contains a N_SUMMARY column. So N_SUMMARY is cross-referencing system allowing users to couple a source to its parent observation.- REVOLUTION (J)
The chronological orbit number since the launch of the XMM mission. The XMM-Newton orbital period is 48 hours. The ingested catalogue data range from 39 &get; REVOLUTION &get; 1337.- OBSID (10A)
Each XMM pointing has an exclusive 10-digit observation identification number or OBSID. This column contains the OBSID of the observation from which the source detection originates.- TARGET (20A)
The nominal science target of each observation.- FILTERS (30A)
The instrument filters used during the observation and which yielded source detections. The list will contain one or more of "UVW2", "UVM2", "UVW1", "U", "B", "V". A description of the filter properties is provided in the XMM-Newton User's Handbook. Sources detected through the WHITE, MAGNIFIER, UGRISM and VGRISM filters are not included within the catalogue. Sources without detections in the either of the three UV filters are also excluded (see the Data Selection section).- MJD_START (D) [days]
The Modified Julian Date at the start of the observation, ranging from 51,598 > MJD > 54,188.- MJD_END (D) [days]
The Modified Julian Date at the end of the observation.- RA_PNT (E) [degrees]
The Right Ascension (J2000) of the nominal OM boresight pointing during the observation.- DEC_PNT (E) [degrees]
The Declination (J2000) of the nominal OM boresight pointing during the observation.- RA_PNT_HMS (13A)
Hours-minutes-seconds rendition of RA_PNT.- DEC_PNT_HMS (14A)
Degrees-arcminutes-arcseconds rendition of DEC_PNT.- EXPOSURE_MIN (J) [seconds]
The minimum exposure time from the sample of OM exposures during the observation.- EXPOSURE_MAX (J) [seconds]
The maximum exposure time from the sample of OM exposures during the observation.- N_SOURCES (J)
The total number of individual sources detected during the observation.- N_SOURCES_FILTER (J)
The total number of individual sources detected during the observation through the specified instrument filter.- RAOFFSET (E) [arcsec]
The onboard pointing knowledge of the XMM spacecraft is good to within a few arcsec. To improve upon this, ground-processed astrometric corrections are performed on the OM source positions by cross-correlating with the USNO-B1.0 survey. The offset correction in the RA direction is provided in this column. Details of this correction procedure are described in the Data Processing section. Note that currently, the XMM pipeline products contain source lists that have been astrometrically corrected. They do not, however, contain corrected sky images (Known Issues).- DECOFFSET (E) [arcsec]
The onboard pointing knowledge of the XMM spacecraft is good to within a few arcsec. To improve upon this, ground-processed astrometric corrections are performed on the OM source positions by cross-correlating with the USNO-B1.0 survey. The offset correction in the Dec direction is provided in this column. Details of this correction procedure are described in the Data Processing section. Note that currently, the XMM pipeline products contain source lists that have been astrometrically corrected. They do not, however, contain corrected sky images (Known Issues).- RAOFFSET_ERR (E) [arcsec]
The statistical 1σ uncertainty coupled to RAOFFSET.- DECOFFSET_ERR (E) [arcsec]
The statistical 1σ uncertainty coupled to DECOFFSET.- OFFSET_RMS (E) [arcsec]
The root mean square of the positional offsets between OM and USNO-B1.0 sources, after a ground-processed astrometric correction has been applied.